This invention relates to wiring means for electrically connecting a plurality of light emitting elements and, in particular, to a wiring board which has an FFC (Flexible Flat Cable) and to a light emitting apparatus which has the wiring board and the light emitting elements mentioned above.
In recent lighting means, in order to realize reduction in size and in weight, electric power saving, improvement in durability and maintainability, reduction in cost, precise control of color tones and luminances, and the like, conventional light emitting means is progressively replaced by a solid-state light emitting element. The conventional light emitting means is, for example, a kind of a vacuum tube, such as an electric bulb and a cold-cathode tube. The solid-state light emitting element is, for example, a LED (Light Emitting Diode) or the like.
As a specific example, a backlight of a liquid crystal display will be considered. For a small-sized display, the LED or EL (Electro Luminescence) has been used for a relatively long time. On the other hand, for a large-sized display, instead of the conventional light emitting apparatus using the cold-cathode tube, an array of a plurality of light emitting apparatuses each of which comprises a plurality of LEDs arranged in an array or in a line has recently become widely used.
Herein, the light emitting apparatus comprising the light emitting elements arranged in a line or in an array has, in addition to the light emitting elements, such as the LEDs, wiring means for electrically connecting the light emitting elements to one another in series or in parallel for the purpose of collectively connecting the light emitting elements to a power source or to a light emission control circuit.
As the wiring means of the light emitting apparatus comprising the light emitting elements arranged in an array, use is made of a printed board provided with a conductive pattern for connecting the light emitting elements to one another.
As the wiring means of the light emitting apparatus comprising the light emitting elements arranged in a line, for example, JP-A-2008-218013 (Document 1) discloses a wiring cable used in a ribbon-like light emitting apparatus for use in an illumination system extended indoors or outdoors. The wiring cable is a kind of a flat harness comprising a plurality of conductive wires parallel to one another and covered with a single sheath or coating. The wiring cable has a plurality of pairs of cutouts formed on lateral sides thereof at a plurality of positions. Then, a plurality of LED modules each of which is integrally formed with a resin holder having a pair of protrusions are fixed to the wiring cable so that the protrusions are fitted to the cutouts.
However, the wiring means using the printed board is required to be designed and manufactured individually for each size of a liquid crystal display. Therefore, the wiring means is low in versatility and disadvantageous in cost performance.
On the other hand, the wiring cable disclosed in Document 1 is assumed to be used in the ribbon-like light emitting apparatus which is changed into various shapes when used. Therefore, the wiring cable is not suitable for a light emitting apparatus which must be manufactured with precise dimensions and be stationarily or fixedly installed, like the backlight of the electronic device such as the liquid crystal display. Additionally, a total thickness of the harness and the resin holder of the LED module becomes a bottleneck in reduction in profile of the liquid crystal display, which is increasingly demanded in recent years.